all i want to do is count the lines in each file

[perfringo]

If I need to have quick look at number of lines in file then I use wc in terminal.

cat my_filename | wc -l

It is easy to use in Python with subprocess. Specific example on file named shakespeare.txt; check_output returns bytes so I converted it into integer:

>>> import subprocess
>>> source = subprocess.Popen(['cat', 'shakespeare.txt'], stdout=subprocess.PIPE)   
>>> lines = int(subprocess.check_output(['wc', '-l'], stdin=source.stdout))     
>>> lines
4155